/*
 * Copyright (c) 2024 Huawei Device Co., Ltd.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { ts, rule } from "qvog-dsl";

const SEVERITY = 2;
const DOC_PATH = 'docs/no-top-level-var.md';
const DESCRIPTION = 'Using var at the top level of a module can lead to variable hoisting and scope pollution. Prefer let or const instead.';
function isTop(node: ts.Node): boolean {
    let parent = node.parent;
    while (parent) {
        if (
            ts.isFunctionDeclaration(parent) ||
            ts.isFunctionExpression(parent) ||
            ts.isArrowFunction(parent) ||
            ts.isMethodDeclaration(parent) ||
            ts.isClassDeclaration(parent) ||
            ts.isBlock(parent) // 可以根据需要排除其他局部块
        ) {
            return false; // 在局部作用域里
        }
        if (ts.isSourceFile(parent)) {
            return true; // 到 SourceFile，说明在顶层
        }
        parent = parent.parent;
    }
    return false;
}
export default rule()
  .match(ts.isVariableStatement)
  .when(node => {
      // 判断声明是否使用 var
      // 获取 declarationList 的 flags
      const flags = node.declarationList.flags;

      // ts.NodeFlags.Const | ts.NodeFlags.Let 都有，var 就没有这些标记
      const isVar = (flags & ts.NodeFlags.Let) === 0 && (flags & ts.NodeFlags.Const) === 0;

      // 判断父节点是否为顶层 SourceFile
      const isTopLevel = isTop(node);

      return isVar && isTopLevel;
  })
  .report({
      severity: SEVERITY,
      description: DESCRIPTION,
      docPath: DOC_PATH,
  });
